Dynamic activities increase intra-abdominal pressure (i.e. coughing, straining) resulting in a corresponding increase in bladder pressure. When this bladder pressure exceeds urethral pressure, stress urinary incontinence occurs. It has been universally acknowledged that our tools for measuring urethral pressure to diagnose stress urinary incontinence are flawed. Current instruments are withdrawn through the length of the urethra with a puller device and can only measure urethral pressure at small discrete points while the urethra is at rest. We are studying a new method (perfused sleeve sensor technology) for directly measuring urethral pressures during dynamic conditions. The sleeve sensor consists of a thin-walled silicone sleeve that is attached to the catheter and is constantly perfused with fluid. The unique quality of this perfused sleeve is its ability to record maximum pressure measurements anywhere along the length of the sleeve without requiring withdrawal of the catheter. Our preliminary data supports the ability of the urethral sleeve sensor to directly measure maximum urethral closure pressure within the urethra both during rest and dynamic activities. Currently there are no objective parameters for surgical cure of stress urinary incontinence; a deficiency in our diagnostic testing capabilities which is widely recognized by pelvic reconstructive surgeons. This two- phase study will determine if sleeve sensor technology can provide an objective urodynamic measure of cure. Phase 1 involves catheter design and optimization. Recruiting 16 continent volunteers will allow us to test the urethral sleeve sensor with different perfusion rates and luminal diameters in order to develop the optimal catheter which will then be used in Phase 2. The primary aim of Phase 2 is to compare the maximum urethral closure pressures during valsalva before and after surgical intervention for stress urinary incontinence with a mid-urethral sling. We hypothesize that urethral closure pressure during valsalva in stress incontinent subjects, as measured using the urethral sleeve sensor, will convert from 0 cm H2O to a positive value after mid-urethral sling surgery. This fundamental definition of incontinence and continence has never been demonstrated with any other urethral pressure technology. Our secondary aim will be to understand the mechanism of pelvic floor contraction for improving urinary continence by correlating vaginal pressure measurements obtained during pelvic floor muscle contractions with urethral pressures using the urethral sleeve sensor. During Phase 2, 34 subjects with stress urinary incontinence desiring surgical therapy will undergo preoperative and postoperative sleeve urodynamic urethral pressure studies as well as vaginal pressure studies. The impact of this study is that we may demonstrate and validate the first physiologic measurement tool of incontinence cure for both research studies and clinical usage.